Prior to insertion of a stent in a bodily vessel, it is typically necessary to polish the stent to eliminate sharp corners on the edges of the stent and to provide as smooth a surface as possible. The presence of sharp edges may directly damage a vessel and may provide a site for collection of plaque and other deposits. Where the stent is balloon expandable, the presence of sharp edges may also lead to balloon bursts. A rough stent surface may result in medical complications such as the formation of thrombi and restenosis.
Other implantable medical devices for which polishing may be beneficial include vena cava filters.
A number of techniques have been used to polish stents and vena cava filters. One such technique involves the use of an abrasive to polish the material from which the stent is formed. Where polishing is not possible prior to stent formation, the formed stent may be polished using abrasives or electropolishing techniques. The use of abrasives to polish a stent is disclosed in U.S. Pat. No. 5,746,691, U.S. Pat. No. 5,788,558, U.S. Pat. No. 5,902,475 and U.S. Pat. No. 6,086,455. An electropolishing technique is disclosed in U.S. Pat. No. 5,344,425. Electropolishing techniques typically polish surfaces to a mean roughness Ra of 300-400 nm. Electropolishing is only suitable on certain surfaces, however, such as stainless steel, copper alloys and aluminum alloys.
Electrpolishing has also been used to polish medical guidewires as disclosed in U.S. Pat. No. 5,178,158.
There remains a need for novel techniques for polishing stents, vena cava filters and medical guidewires which result in smoother surfaces.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The invention in various of its embodiment is summarized below. Additional details of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
In one embodiment, the invention is directed to a method of polishing at least a portion of a stent substrate. The method comprises the steps of providing a stent substrate, providing a laser operating at a wavelength absorbable by the stent substrate and irradiating the surface of the stent substrate with a laser beam from the laser at a wavelength absorbed by the stent substrate to cause a controlled level of melting of the surface of the stent substrate. Finally, the stent substrate is allowed to solidify.
The invention is also directed to a method of polishing at least a portion of a stent substrate comprising the steps of providing a stent substrate, providing a laser operating at a wavelength absorbable by the stent substrate and directing a laser beam output from the laser at a portion of the stent substrate, the laser beam characterized by a fluence of between about 1 J/cm2 and 5000 J/cm2.
The invention is also directed to a method of polishing at least a portion of a stent substrate comprising the steps of providing a stent substrate, providing a laser operating at a wavelength absorbable by the stent substrate and directing a laser beam output from the laser at a portion of the stent substrate, the laser beam melting a surface layer of the stent substrate to a depth of no greater than 5 percent of the thickness of the stent substrate in the portion of the stent substrate impinged by the laser beam.
The invention is further directed to a method of polishing at least a portion of a medical guidewire for use with a catheter. The method comprises the steps of providing a medical guidewire, providing a laser and irradiating the surface of the guidewire with a beam of radiation from the laser at a wavelength absorbed by the guidewire to cause a controlled level of melting of the surface of the guidewire in the portion of the guidewire impinged by the laser beam. Finally, the surface of the guidewire is allowed to solidify.
The invention is also directed to a method of polishing at least a portion of a guidewire comprising the steps of providing a guidewire, providing a laser operating at a wavelength absorbable by the guidewire and directing a laser beam output from the laser at a portion of the guidewire, the laser beam melting a surface layer of the guidewire to a depth of no greater than 5 percent of the thickness of the guidewire in the portion of the guidewire impinged by the laser beam.
The invention is also directed to a method of polishing at least a portion of a component for use with a catheter system. The method comprises the steps of providing the component for use with a catheter system, providing a laser operating at a wavelength absorbable by the component for use with a catheter system and directing a laser beam output from the laser at a portion of the component for use with a catheter system, the laser beam melting a surface layer of the component for use with catheter system to a depth of no greater than 5 percent of the thickness of the component in the portion of the component impinged by the laser beam.